fs/ntfs3: Harden against integer overflows

Smatch complains that the "add_bytes" is not to be trusted.  Use
size_add() to prevent an integer overflow.

Fixes: be71b5c ("fs/ntfs3: Add attrib operations")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

Author: Dan Carpenter

fs/ntfs3/xattr.c

@@ -107,7 +107,7 @@ static int ntfs_read_ea(struct ntfs_inode *ni, struct EA_FULL **ea,
 		return -EFBIG;
 
 	/* Allocate memory for packed Ea. */
-	ea_p = kmalloc(size + add_bytes, GFP_NOFS);
+	ea_p = kmalloc(size_add(size, add_bytes), GFP_NOFS);
 	if (!ea_p)
 		return -ENOMEM;